Mariners’ Johjima out 2-3 weeks with hamstring strain

The Mariners keep winning games, but losing players, the only troubling trade-off in a season that has otherwise gotten off to a remarkably smooth start.

Catcher Kenji Johjima went on the 15-day disabled list with a strained right hamstring Thursday, a day after starting pitcher Ryan Rowland-Smith suffered the same fate with a tendon problem in his throwing arm.

The club also optioned infielder Matt Tuiasosopo to AAA Tacoma and brought right-handed reliever Sean White up to the big-league club to bolster the bullpen while Chris Jakubauskas fills Rowland-Smith’s spot in the rotation for at least two starts.

Rob Johnson, the M’s 26-year-old rookie backstop, becomes the new starter and was immediately inserted into Thursday’s lineup in the No. 8 hole by manager Don Wakamatsu, who also is resting Ken Griffey Jr. and Franklin Gutierrez while starting Mike Sweeney at DH and Wladimir Balentien in left field.

Johjima left Wednesday’s game in the bottom of the fourth inning after experiencing tightness in his leg while running out his go-ahead RBI single. Mariners doctor Edward Khalfayan examined Johjima Thursday and said he has a Grade 1 strain, the least damaging grade of injury on a scale of 1 to 3.

Johjima said he initially felt a problem with the leg on defense in the top of the fourth.

“I felt discomfort the inning before when I was covering first base,” he said.

Johjima said he’s never had hamstring problems and hasn’t been on the disabled list since his days in Japan, when he broke his collarbone and shin in separate instances.

“They say a lot of the fast runners have this type of injury, so I’m not sure why I’m getting this,” Johjima said through a translator, poking fun at his own lack of speed.

Johjima was limping badly in the clubhouse and said he’s in considerable pain, both from the injury and the timing.

“It is very disappointing to leave the team at this time when we’re playing so good and now with Ichiro back in the lineup,” he said.